/* ------------------------------------------------------------------------
 *
 * geqo_cx.cpp
 *
 * Portions Copyright (c) 2020 Huawei Technologies Co.,Ltd.
 *	 cycle crossover [CX] routines;
 *	 CX operator according to Oliver et al
 *	 (Proc 2nd Int'l Conf on GA's)
 *
 * src/gausskernel/optimizer/geqo/geqo_cx.cpp
 *
 * -------------------------------------------------------------------------
 */
/* contributed by:
   =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
   *  Martin Utesch				 * Institute of Automatic Control	   *
   =							 = University of Mining and Technology =
   *  utesch@aut.tu-freiberg.de  * Freiberg, Germany				   *
   =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
 */
/* the cx algorithm is adopted from Genitor : */
/*************************************************************/
/* 															 */
/* 	Copyright (c) 1990										 */
/* 	Darrell L. Whitley										 */
/* 	Computer Science Department								 */
/* 	Colorado State University								 */
/* 															 */
/* 	Permission is hereby granted to copy all or any part of  */
/* 	this program for free distribution.   The author's name  */
/* 	and this copyright notice must be included in any copy.  */
/* 															 */
/*************************************************************/

#include "postgres.h"
#include "knl/knl_variable.h"
#include "optimizer/geqo_recombination.h"
#include "optimizer/geqo_random.h"

/* cx
 *
 *	 cycle crossover
 */
int cx(PlannerInfo* root, Gene* tour1, Gene* tour2, Gene* offspring, int num_gene, City* city_table)
{
    int i, start_pos, curr_pos;
    int count = 0;
    int num_diffs = 0;

    /* initialize city table */
    for (i = 1; i <= num_gene; i++) {
        city_table[i].used = 0;
        city_table[tour2[i - 1]].tour2_position = i - 1;
        city_table[tour1[i - 1]].tour1_position = i - 1;
    }

    /* choose random cycle starting position */
    start_pos = geqo_randint(root, num_gene - 1, 0);

    /* child inherits first city  */
    offspring[start_pos] = tour1[start_pos];

    /* begin cycle with tour1 */
    curr_pos = start_pos;
    city_table[(int)tour1[start_pos]].used = 1;

    count++;

    /* cx main part */
    /* STEP 1 */
    while (tour2[curr_pos] != tour1[start_pos]) {
        city_table[(int)tour2[curr_pos]].used = 1;
        curr_pos = city_table[(int)tour2[curr_pos]].tour1_position;
        offspring[curr_pos] = tour1[curr_pos];
        count++;
    }

    /* STEP 2 */
    /* failed to create a complete tour */
    if (count < num_gene) {
        for (i = 1; i <= num_gene; i++) {
            if (!city_table[i].used) {
                offspring[city_table[i].tour2_position] = tour2[(int)city_table[i].tour2_position];
                count++;
            }
        }
    }

    /* STEP 3 */
    /* still failed to create a complete tour */
    if (count < num_gene) {
        /* count the number of differences between mom and offspring */
        for (i = 0; i < num_gene; i++) {
            if (tour1[i] != offspring[i]) {
                num_diffs++;
            }
        }
    }

    return num_diffs;
}
